Debian – multiple monitors and multiple GPUs

TL;DR:

Background Ramble

So I had my system running nicely on both Windows and Linux (Debian GNU/Linux 8 with KDE), triple monitors all running off my GTX1080. Along comes Oculus and changes their implementation so you can only use “Desktop Pull-out” if you have less than 3 monitors plugged in. Fixed that by moving one of my monitors onto the integrated GPU; I only need my main monitor on the NVidia card for gaming.

This also meant moving monitors around on the outputs so that my main monitor would display the BIOS etc. (the side monitors are rotated 90 degrees).

Not surprisingly Linux needed some post-bootup configuration, and somewhat surprisingly it took quite a bit of searching to find the magic invocations this time around. The magic program itself is xrandr, nobody should be using an Xorg.conf in this day and age.

Step 1 – List Providers

First things, listing the number of “providers” (ie, graphics cards) in your system: